Скачать с ютуб ICSE Class 9 Physics|Chapter 9 ||Current Electricity| в хорошем качестве

ICSE Class 9 Physics|Chapter 9 ||Current Electricity|

#IcsePhysicsClass9 A cell is a single electrical energy source which uses chemical reactions to produce a current. An electrical cell is an 'electrical power supply'. It converts stored chemical energy into electrical potential energy. A cell is a single electrical energy source which uses chemical reactions to produce a current. An electrical cell is an 'electrical power supply'. It converts stored chemical energy into electrical potential energy. Primary and Secondary Cells • Primary cells are basically use-and-throw galvanic cells. The electrochemical reactions that take place in these cells are irreversible in nature. Hence, the reactants are consumed for the generation of electrical energy and the cell stops producing an electric current once the reactants are completely depleted. • Secondary cells (also known as rechargeable batteries) are electrochemical cells in which the cell has a reversible reaction, i.e. the cell can function as a Galvanic cell as well as an Electrolytic cell. • Most of the primary batteries (multiple cells connected in series, parallel, or a combination of the two) are considered wasteful and environmentally harmful devices. This is because they require about 50 times the energy they contain in their manufacturing process. They also contain many toxic metals and are considered to be hazardous waste. Potential and Potential Difference Flow of electrons between the conductors: When two charged conductors are joined by a metallic wire or they are placed in contact, the free electrons flow from a conductor having more concentration of electrons to the conductor having less concentration of electrons. Potential and Electric Current  Potential is an electric state of a conductor which determines the direction of flow of charge when the two conductors are either kept in contact or joined by a metallic wire.  The electric current flows from a region of higher potential to a region of lower potential, i.e., in a direction opposite to the direction of flow of electrons. Potential as work done per unit charge:  The potential at a point is defined as the amount of work done in bringing a unit positive charge from infinity to that point  The work needed to move a charge Q from infinity to a point P where electric potential is V will be: W = QV  The S.I. unit is joule/coulomb (or J/C-1) Potential Difference:  The potential difference (p.d.) between two points is equal to the work done in moving a unit positive charge from one point to the other.  It is a scalar quantity.  VA – VB = W/Q, where W is the work done in moving a test charge Q coulomb from a point A to the point B and VA and VB are the potentials at point A and B.  The S.I. unit is JC-1. Resistance  The resistance of a conductor depends on the number of collisions suffered by the electrons with the positive ions in moving from one end to the other end.  Resistance of wire (R) = V/l.  It’s S.I. unit is ohm and its symbol is ?.  When conductors are joined in series, the total resistance increases.  When conductors are joined in parallel, the total resistance decreases. A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. In electrical circuits, resistors are generally connected in two ways: 1. Series combination of resistors: If a number of resistors are joined end to end in an electric circuit, the resistors are said to be connected in series. 2. Parallel combination of resistors: If resistors are connected across same ends and the potential difference across each of them is the same, then the resistors are said to be connected in parallel. The current is divided between all the resistors connected in parallel. In this lesson, you will learn about resistors that are connected in series and in parallel. Resistors in Series  The current has a single path for its flow i.e. same current passes through each resistor.  The potential difference across any resistor is directly proportional to its resistance.  The potential difference across the entire circuit is directly proportional to its resistance and is equal to the sum of potential differences across the individual resistor.  V=V1+V2+V3V=V1+V2+V3  The equivalent resistance (Rs) is equal to the sum of individual resistance.  Rs=R1+R2+R3Rs=R1+R2+R3 Secondary cells are cells which provide current as a result of reversible chemical reactions. It converts electrical energy into chemical energy when current is passed in it (i.e. during charging), while it converts chemical energy into electrical energy when current is drawn from it (i.e., during discharging). Example: Lead (or acid) accumulator. The substances which allow electric current to flow through them easily are called conductors. Examples: Impure water and metals. The substances which do not allow the electric current to flow through them are called insulators. Examples: Rubber and wood. Conductor has a large no of free e